Increasing need for light weight furniture has lead to the development of "A-surface" fabrics, i.e. fabrics which form both a covering and elastomeric supporting web, eliminating the use of bulky cushioning materials such as polyurethane foam. Demand for improvements in strength retention of A-surface fabrics lay the groundwork for the present invention.
A-surface fabrics used in furniture which incorporate elastomeric monofilaments derive essentially their sole strength. and stretch recovery properties from the structural elastomeric monofilaments having deniers in the 300 to 3000 range. See: U.S. Pat. Nos. 4,545,257, 4,842,257, 5,013,089, 5,533,789, and 5,596,888 for example.
There have been provided heretofore stabilizer systems to improve aging properties of elastomeric copolyesters. U.S. Pat. Nos. 3,651,014; 3,763,109; and 3,766,146, granted Mar. 21, 1972, Oct. 2 and Oct. 16, 1973, respectively, all to Witsiepe disclose certain copolyetherester elastomers which can be used alone or in combination with each other as one of the materials of construction in woven furniture support material.
British Pat. No. 1,458,341, published Dec. 15, 1976 to Browm et al, discloses an orientation and heat-setting process for treating copolyetherester elastomers, which process is conveniently and beneficially used to treat the elastomers disclosed by Witsiepe in the above mentioned U.S. Pat. No. 3,766,146. The heat-setting process of Brown can be used to treat filaments of Witsiepe's copolyetherester elastomers which can be subsequently used in the woven furniture support material.
Heterofilaments are included within the monofilaments herein, such as sheath-core monofilaments. U.S. Pat. No. 4,136,715, granted Jan. 30, 1979 to McCormack et al, discloses composite monofilaments of different copolyetherester elastomers having melting points differing from each other by at least 20.degree. C. Such composite monofilaments can be used in the woven furniture support material of the present invention and are conveniently formed as a "sheath/core" monofilament having a core with higher M.P. than the sheath. However, further improvement in the retention of monofilament physical properties are needed when the end-use includes long term exposure to environmental elements.
Various stabilization means for copolyetherester polymers are known. In U.S. Pat. No. 4,136,090, for example, thermoplastic copolyetherester elastomers are stabilized against heat and light aging by incorporating into the copolyetherester polymer an effective concentration of a phenolic antioxidant and a copolyester containing a hindered amine moiety having the structure: ##STR2## wherein A is ethylene and or propylene, X is a divalent hydrocarbon radical of 2 to 18 carbons and (n+m) equals 5 to 40 and wherein (I) is connected to ester units in the copolyetherester. Although the molecular weight of the bound hindered amine moiety renders it non-migratory, it would be advantageous to provide a higher molar concentration of hindered amine moiety in a lower weight percentage addition of a copolyester so as to retain higher physical properties for a monofilament containing a hindered amine stabilizer material.
Japanese Patent Publication No. 75/91652 discloses the use of a number of hindered piperidine type photostabilizers in combination with phenolic antioxidants in copolyetheresters. However, it has been previously noted, according to U.S. Pat. No. 4,185,003, that when the teaching of this Japanese Publication is followed, photostabilization is improved however heat-aging behavior is worsened (see, column 1, lines 30-45 of U.S. Pat. No. 4,185,003). The improvement taught in U.S. Pat. No. 4,185,003 is the combination with the copolyester with phenolic antioxidant and hindered amine having the structure: ##STR3## where R is hydrogen or an alkyl radical of 1-12, preferably 1-4 carbon atoms and R.sub.2 and R.sub.3 represent an alkyl radical hydrocarbons. The use of a hindered amine such as (II) is likely to exhibit a widely varying degree of performance in a monofilament which undergoes a heat-setting treatment at 300.degree. C. which has the tendency to distort the monofilament.
In U.S. Pat. No. 4,340,718, polyester materials, particularly copolyesters, are rendered less susceptible to weathering by incorporating into the polyester resin a dimethyl and diethyl ester of p-methoxybenzylidenemalonic acid having monofunctional terminal ester forming groups or a difunctional comonomer.
U.S. Pat. Nos. 4,355,155 and 4,405,749 each disclose segmented thermoplastic copolyester elastomers which may be stabilized against heat. For example, in U.S. Pat. No. 4,355,155 such stabilizers may include phenols and their derivatives, amines and their derivatives, compounds containing both hydroxyl and amine groups, hydroxyazines, oximes, polymeric phenolic esters and salts of multivalent metals in which the metal is in its lower state (see column 3, lines 46-52), while in U.S. Pat. No. 4,405,749, a particular triazine-based anti-oxidant (i.e., 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid triester with 1,3,5-tris-(2-hydroxyethyl)-s-triazine-2,4,6-(1H, 3H, 5H) trione) is disclosed as having superior thermal stability.
Each of the compositions of the above prior issued U.S. patents moreover mention that additional stabilization against ultraviolet light may be obtained by compounding the copolyetheresters with various UV absorbers, such as substituted benzophenones or benzotriazoles (see, column 4, lines 1-3 of U.S. Pat. No. 4,355,155; and column 4, lines 10-13 of U.S. Pat. No. 4,405,749).
U.S. Pat. No. 4,524,165 discloses a combination of certain copolyesterether with at least one hindered phenolic antioxidant, at least one ultraviolet light stabilizer compound which is compatible with the specific copolyesterether, and at least one hindered amine having the formulas: ##STR4## wherein m and n are integers from 1 to 20, R.sub.1-4 are each independently selected from hydrogen, substituted or unsubstituted alkyl, aryl, alkylene, cycloalkylene, hydroxyalkylene, and esters of hydroxyalkylene, and alkylenecarboxylic acid and esters, amides and metal salts of said alkylenecarboxylic acid. The ultraviolet light stabilizers suggested include monomeric benzotriazoles and monomeric benzophenones. The particular copolyetheresters having superior weathering ability are derived from 1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol, a polyalkylene ether glycol, as compared to terephthalate-based polyesters. In weathering exposure comparisons of stabilized inventive copolyesterethers; versus the terephthalic acid types containing the same stabilizer combinations, the terephthalate types performed significantly worse (rapid aging) than the polyesterethers derived from 1,4-cyclohexane dicarboxylic acid and 1,4-cyclohexane dimethanol. It would be desirable to provide terephthalate-based polyester which exhibit improved aged retention of physical properties, as these types of polyesters are more abundant and economical.
Blends of polybutylene terephthalate and a segmented thermoplastic copolyester elastomer are stabilized against heat, or ultraviolet light in known manner via the addition of various stabilizers. For example, in U.S. Pat. No. 3,907,926, antioxidants and amide stabilizers may be incorporated into the PBT/polyester elastomer blends (see column 6, line 55 bridging column 7, line 25), while U.S. Pat. No. 4,469,851 suggests the phenol derivatives (including 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid triester with 1,3,5-tris-(2-hydroxyethyl)-s-triazine-2,4,6-(1H, 3H, 5H) trione) may be incorporated into the PBT/polyester elastomer blends for UV-light stabilization functions.
Two considerations are needed to understand sources of failure in phthalate-based copolyesters as monofilament/multifilament composite fabric structural arrays for seating components which are exposed to heat and light. Firstly, the heat stabilizing ability during processing of the fiber and UV resistance under long term UV exposure, and secondly the resistance to heat setting treatments above the HDT of the monofilament used to provide bonding of multifilament yarns to the structural warp and/or weft monofilament fibers. In aging studies there have been evidenced serious consequences from weather aging in terms of retention of strength and elongation properties for heat-set elastomeric phthalate-based monofilament. Furthermore the temperatures required to achieve adequate heat set bonding with multifilament yarns can cause reversion of the polymer as well as redistribution and/or deactivation of the stabilizer system resulting in deleterious effects. The redistribution and/or deactivation has significant effects on long term retention of tensile strength and elongation after the equivalent of long-term exposures to UV irradiation. Specifically, conventionally stabilized terephthalate-based monofilaments which have been heat set exhibit up to 50% loss in tensile strength and elongation properties after exposure up to 451 kilojoules per square meter of irradiation under standard test SAE J-1885. It would be of industrial importance to provide elastomeric structural fibers for furniture support materials A-surface fabrics which can retain a higher proportion, i.e., at least about 85% or higher of the unaged tensile and elongation after heat setting and exposure to 481 KJ under SAE J-1885.
It would be of commercial importance to obtain durable phthalate-based copolyester monofilaments which have improved aging retention of physical properties for seating fabrics made therefrom which have been heat-set and will be exposed on a long term basis to UV irradiation. Furthermore it would be of industrial importance to provide a stabilized elastomeric copolyetherester monofilament that will exhibit high strength, and aged strength retention, low creep (shape and size retention), acid and chlorine resistance, and weathering resistance, even after the fabric heat-setting treatment.